Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$154.97	10.702%	$171.5549	$171.55	$171.55	$171.60
Purchase #2	$184.58	11.328%	$205.4892	$205.49	$205.50	$205.50
Purchase #3	$144.65	13.563%	$164.2689	$164.27	$164.25	$164.30
Purchase #4	$213.30	11.526%	$237.885	$237.89	$237.90	$237.90
Purchase #5	$214.61	11.263%	$238.7815	$238.78	$238.80	$238.80
Purchase #6	$176.45	12.766%	$198.9756	$198.98	$199.00	$199.00
Purchase #7	$222.51	10.514%	$245.9047	$245.90	$245.90	$245.90
7 purchase totals =	$1,311.07		$1,462.8598	$1,462.86	$1,462.90	$1,463.00